1.0.48.8: better binary stream support in RUN-PROGRAM

  * In COPY-DESCRIPTOR-TO-STREAM, decode octets only if the stream has
    a character element type.

    For :DEFAULT and (UNSIGNED-BYTE 8) just copy the octets over
    directly.

    For others, signal an error. (Would be nice to support, but not a
    high priority.)

  * Similarly for copying to temporary files from non-fd input
    streams.